This invention relates to an improved iron-based oxygen and carbon dioxide absorbent and method for storing coffee powder or beans using such absorbent.
Roasted coffee powder or beans are oxidized and become less fresh during storage. An attempt has been made to place them in a package filled with an inert gas, but because of incomplete oxygen elimination, the product is not satisfactorily prevented from deteriorating. In addition, because of the pressure of carbon dioxide generated from the roasted beans, the package bulges greatly until it breaks.
Most foods can be completely and advantageously protected by an iron-based oxygen absorbent from the deleterious effect of oxygen. But in spite of the presence of an oxygen absorbent, roasted coffee powder or beans in a package generate a great amount of carbon dioxide whose pressure increases to such an amount that the package may break. Besides, the roasted coffee powder or beans have a very low water activity. Most oxygen absorbents have low ability to absorb oxygen in a dry atmosphere, and their ability to absorb oxygen is also decreased in the presence of carbon dioxide. It has been therefore difficult to store roasted coffee powder or beans with an oxygen absorbent. Carbon dioxide may be removed from the package of roasted coffee powder or beans with a CO.sub.2 absorbent such as alkaline substances, but when the alkali contacts iron powder used as an oxygen absorbent, the rate of O.sub.2 absorption by iron powder becomes slow, particularly when it is contacted by a liquid alkali or alkali powder. As already stated, roasted coffee powder or beans generate a large amount of CO.sub.2 and have a very low water activity, so they must be stored by an oxygen absorbent whose absorbability is not decreased in a dry atmosphere or in the presence of CO.sub.2 and which can prevent breakage of the package by carbon dioxide generated from coffee powder or beans packed in the package.